tcp/dccp: warn user for preferred ip_local_port_range
After commit 07f4c90062f8f ("tcp/dccp: try to not exhaust
ip_local_port_range in connect()") it is advised to have an even number
of ports described in /proc/sys/net/ipv4/ip_local_port_range
This means start/end values should have a different parity.
Let's warn sysadmins of this, so that they can update their settings
if they want to.
Suggested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index e648927..0330ab2 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -45,7 +45,13 @@
/* Update system visible IP port range */
static void set_local_port_range(struct net *net, int range[2])
{
+ bool same_parity = !((range[0] ^ range[1]) & 1);
+
write_seqlock(&net->ipv4.ip_local_ports.lock);
+ if (same_parity && !net->ipv4.ip_local_ports.warned) {
+ net->ipv4.ip_local_ports.warned = true;
+ pr_err_ratelimited("ip_local_port_range: prefer different parity for start/end values.\n");
+ }
net->ipv4.ip_local_ports.range[0] = range[0];
net->ipv4.ip_local_ports.range[1] = range[1];
write_sequnlock(&net->ipv4.ip_local_ports.lock);